(1) Field of the Invention
The present invention relates to an apparatus for recording acoustic signals from an underwater transducer and more particularly to a self-powered, silent, digital storage device enclosed in a sealed case and having a preselectable time delay circuit and a relatively large storage capacity.
(2) Description of the Prior Art
Digital recording devices such as magnetic tape, magnetic disk, impact printer, thermal printer and paper punch are commonly used for permanently storing digital information until such data can be processed and analyzed. Each above storage medium has inherent advantages and disadvantages which affect selection for a particular end use. For example, when considering a digital recorder for use with a remote acoustic sensor, an important criteria is that the device not generate an acoustic signal during operation which would be detectable by its own sensor, thus adding an unwanted noise signal to the data or masking the sought information completely. Unfortunately, the above described recording devices all rely upon mechanical motion to store data, the motion being provided by either an electric motor or a solenoid. These mechanical devices though generate vibrations in the acoustic frequency range of the sensor and self-contaminate the information being recorded. What is desirable is a non-volitile data storage medium which records data silently.